Process for preparing photographic silver halide emulsions for multicolor photography



' :raphic color images.

Patented Feb. 29, 1944 I PROCESS FOR PREPARING PHOTOGRAPHIC SILVERHALIDE EMULSIONS FOR MULTI- COLOR PHOTOGRAPHY Alfred Friihlich andWilhelm Schneider, Dessau,

and Gustav Wilmanns, Wolfen, Kreis Bitter- !eld, Germany, assig'nors toGeneral Aniline & Film Corporation, New York, N. Y., a corpora- I tionof Delaware No Drawing. Application July 13, 1940, Serial No. 345,364.In Germany July 13, 1939 8 Claims.

The present invention relates to color photosraphy and more particularlyto an improved method of preparing photographic silver-halide emulsionsfor multi-color photography.

It is known that color formers fast to difiusion .re employed for themanufacture of photo- These color formers fast difiusion cannot beremoved from the emul- :ion layer by the usual photographic treatingmaths, for instance by washing, though they have men added to the silverhalide emulsion in dissolved form. As such color formers there wereproposed for instance substances which are insoluble in aqueousalkalies, the hydrogen ion concentration of which correspondsapproximately to that of the usual photographic developing solutions,which, however, are soluble at increased alkalinity, for instance indiluted caustic soda solution. These, color formers are incorporatedinto the emulsion dissolved in diluted caustic soda solution. It isknown furthermore to dissolve scarcely soluble components in organicsolvents, for instance methanol partly with the aid of caustic alkaliesand to add thesesolutions to the photographic emulsion, therebyaccomplishing the necessary dispersion of the precipitated diflicultlysoluble substance in the solution by means of violent stirring or bymeans of precipitating or dispersing agents.

I If there are employed color formers fast to diffusion which containgroups effecting better water solubility, such as acidor hydroxylgroups, they may be dissolved in diluted soda solution, whereby thesesoda-alkaline solutions possess a a pH-value which approximatelycorresponds to that of the photographic developing solution. ThispH-value amounting to about 11, is, however, not very suitable forphotographic emulsions, especially for sensitized emulsion layers, sincethe addition of the solution of the color former influences-thepH-value. This causes nearly always an increasein sensitivity which,however, is entirely undesired at this moment, as the process is hardtocontrol. Such highly sensitive emulsions, moreover, are inclined tofogging and possess low keeping quality.

The present invention has for an object to provide color componentswhich are soluble in the emulsion layer and which are fast to diffusionwith respect to the difierent photographic treating processesafterwards.

A further object is to provide silver halide emulsions containing thecolor forming components fast to diflusion. Y

A further object is to provide an improved film for color photographyhaving superposed silver halide emulsion layers, each layer containing acolor component fast to difiusion.

These and other objects will become apparent from the followingspecification.

It has been found, that these difficulties can be avoided and thatexcellent stable emulsions for multi-color photography are obtained, ifa pH- value of about 5-8 is chosen for the finished emulsion layers. Forthat purpose it is first of all necessary that the color formers fast todifiusion which are to be added to the emulsion are soluble at apH-value of less than 9. To dissolve therefore these components analkalinity must be sufficient which in no case is higher than pH=9. Inorder to accomplish the desired solubility with regard to colorcomponents fast to difiusion, the kind and number of the groups whicheffect improved water-solubility and which have to be introduced intothe molecule, have to be chosen according to the kind and number of themolecule radicals which effect fastness to diffusion.

Such color formers fast to difiusion which possess molecule-radicals andacid groups incorporating fastness to difiusion or which have othersubstituents efiecting sodaor water-solubility are for instance thefollowing: l-naphthol-Z-carboyl amino phenyl-3'-octadecylamino-4'-sulfoacid- 4 -sulfo acid, 1naphthol-2-carboylaminophenyl-3-octadecylamino-4'-carboxylic acid 4-sulfo acid, 1-naphthol-2-carboylaminophenyl-3- oleylamin'o-4'-sulfoacid-4-sulio acid, l-naph- I thol- 2-carboy1aminophenyl-3'-d0decylamin0-4'- thol-2-carboylamino-3'sulfooleylaminobenzene- 4-sulfo acid, di-1,-1-naphthoxy-2,2'-carboyl-3-stearylamino benzidine 4,4 sulfo acid, 1,2,3-

xylenolcarboyloctadecylamino 4 sulfo acid, 1-

naphthol 6 sulfurylheptadecylamino 4 sulfo acid, 6 methoxy-l-naphthol 2carboyl-sulfooleylamino- 4 -su1f0 acid, l-naphthol- 2 -carboylamino4-methylhepta decylaminobenzene-3'- sulfo acid-4'-sulfo acid,l-naphthol-2-carboy1 aminoAFmethylsulfo octadecylaminobenzene- 4-sulfoacid, 8-octadecylethylamino-l-naphthol- 2,4-disulfo acid, mixture froma-oxynaphtholc acid and polyethyleneoxide, mixture from a-oxynaphthoicacid 'and aminophenylpolyethyleneoxideether, 4sulfooleylaminobenzoylacetylamino 3,4' benzenedicarboxylic acid,laurylacetic acid aminebenzenedicarboxylic acid, 1-(3,6'-dimethyl-3-stearoylamino) phenyl-3-methyl-5- pyrazolone-4'-sulfo acid,1,3'-carboxyphenyl- 3- 4'-sulfooleylaminophenyl-5-pyrazolone,1,5'-carboxy- 3' sulfooleylaminophenyl- 3 -,furfuryl- 5 pyrazolone,l-phenyl- 3 -palmitoyl-5-pyrazolone- 3',5-disulfo acid,1-plienyl-3-palmitoyl-5-pyrazolone-3-sulfo acid 4'-methylaminoethanesulfo acid, l-phenyl- 3 -sulfoheptadecyl- 5-pyrazolone, 1,3'-sulfoo1eylaminophenyl- 3 -methyl-5-pyrazo-.

lone, 1,3-sulfooleylaminophenyl 5-pyrazolone-3- acetic acid,5-pyrazolone-3-acetic acid-l-(p-octadecyl-a-carboxylic acid) Colorformers fast to difiusion according to the below-mentioned U. S. patentsare, generally speaking, very suitable, the solubility of which has beenset by the introduction of groups efiecting improved water solubility toa pH-value being smaller than 9: 2,178,612, of November 7,

1939; 2,179,238, of 'November 7, 1939; 2,179,244, of November 7, 1939;2,186,732, of January 9, 1940; 2,186,849, of January 9, 1940; 2,186,850,of January 9, 1940; 2,280,722 of April 21, 1942; 2,307,399,

January 5, 1943.

The components may also be dissolved at a stronger alkalinity thanpH-value=9 and the so lution may then be set at a pH-value of at leastnot more than'9 by adding diluted acid. Furthermore the solution of acolor former having stronger alkalinity may be added to the emulsionduring the manufacturing process or before casting and there may beadded to the emulsion so much of a diluted acid or of an acid salt, asis necessary for the neutralization of the alkali which is not bound tothe color former, Condition is, however, in all these cases, that thecolorformers are soluble at a pH-value of less than 9.

The emulsionsnaturally may contain all modifying agents suitable for themanufacture ofphotographic emulsions. With regard to the final 2,343,051I I V the effect of the to be taken into considermodifying agents haspH-value of the emulsion, also ation.

- We claim:

= 1. Process for the manufacture of silverhaiide emulsions for colorphotoxraphy. which process comprises dissolving in alkali, colorcomponents fast to diflusion in gelatin and completely soluble at a pHvalue of about 9, incorporating the alkaline color former solution intothe emulsion at a pH of about 9, and reducing the alkalinity of themixture by neutralizing to a pH value of from 5 1:08.

2. The process as defined in claim 1, wherein the color component isfast to diffusion by virtue of the presence therein of a long aliphaticchain.

3. The process as defined in claim 1, wherein the color component isfast to diffusion by virtue of the presence therein of a long aliphaticchain and wherein the color component contains a plurality ofwater-solubilizing groups.

4. The process as defined in claim 1, wherein the color component isfast to diffusion by virtue of the presence therein 01 a long aliphaticchain and wherein the color component contains a plurality of sulfonicacid groups.

5. The process as defined in claim 1, wherein the color component is anaphthol containing a long aliphatic chain.

6. The process as defined in claim 1, wherein

